boards: adafruit: Fix ws2812 pin on Adafruit Feather RP2040.

[projektecke]

Description

boards: adafruit: Fix ws2812 pin on Adafruit Feather RP2040.

As stated in [1], the ws2812 pin is on GPIO16.

[1] https://github.com/adafruit/Adafruit-Feather-RP2040-PCB/blob/main/Adafruit%20Feather%20RP2040%20pinout.pdf

Tests executed

Verified on Adafruit Feather RP2040: now the samples/drivers/led/led_strip sample makes the Neopixel LED blink in different colors.

[github-actions]

Hello @projektecke, and thank you very much for your first pull request to the Zephyr project!
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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Hi @projektecke!
Congratulations on getting your very first Zephyr pull request merged 🎉🥳. This is a fantastic achievement, and we're thrilled to have you as part of our community!

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Thank you for your valuable input, and we look forward to seeing more of your contributions in the future! 🪁